The Streptococci make up a medically important genera of microbes known to cause several types of disease in humans, including, for example, otitis media, conjunctivitis, pneumonia, bacteremia, meningitis, sinusitis, pleural empyema and endocarditis, and most particularly meningitis, such as for example infection of cerebrospinal fluid. Since its isolation more than 100 years ago, Streptococcus pneumoniae has been one of the more intensively studied microbes. For example, much of our early understanding that DNA is, in fact, the genetic material was predicated on the work of Griffith and of Avery, Macleod and McCarty using this microbe. Despite the vast amount of research with S. pneumoniae, many questions concerning the virulence of this microbe remain. It is particularly preferred to employ Streptococcal genes and gene products as targets for the development of antibiotics.
The frequency of Streptococcus pneumoniae infections has risen dramatically in the past 20 years. This has been attributed to the emergence of multiply antibiotic resistant strains and an increasing population of people with weakened immune systems. It is no longer uncommon to isolate Streptococcus pneumnoniae strains which are resistant to some or all of the standard antibiotics. This has created a demand for both new anti-microbial agents and diagnostic tests for this organism.
While certain Streptococcal factors associated with pathogenicity have been identified, e.g., capsule polysaccharides, peptidoglycans, pneumolysins, PspA Complement factor H binding component, autolysin, neuraminidase, peptide permeases, hydrogen peroxide, IgA1 protease, the list is certainly not complete. Moreover, very little is known concerning the temporal expression of such genes during infection and disease progression in a mammalian host. Discovering the sets of genes the bacterium is likely to be expressing at the different stages of infection, particularly when an infection is established, provides critical information for the screening and characterization of novel antibacterials which can interrupt pathogenesis. In addition to providing a fuller understanding of known proteins, such an approach will identify previously unrecognised targets.
PhoH is a phosphate starvation-inducible gene that, in at least one or more species, belongs to the phosphate (pho) regulon and has ATP-binding activity (Kim, S. K., Makino, K., Amemura, M., Shinagawa, H. and Nakata, A. (1993) J. Bacteriol. 175 (5), 1316-1324. (See also, Metcalf, W. W., Steed, P. M. and Wanner, B. L. (1990) J. Bacteriol. 172 (6), 3191-3200.) Two transcriptional initiation sites (P1 and P2) have been identified. The upstream P1 promoter contains a pho box, the conserved sequence shared by the pho regulon genes.
In terms of cellular content, phosphate (P) is the third most abundant element. P compounds serve as major building blocks of innumerable biomolecules and it is incorporated into many proteins posttranslationally. P compounds are also especially important in energy metabolism because of the biological role of high-energy phosphoanhydride bonds. Therefore, P metabolism involves numerous metabolic pathways, in addition to those that may have a specific role of assimilating P from the environment and has a vital role in bacterial survival. Inhibitors of proteins involved in phosphate metabolism and its regulation could prevent the bacterium from establishing and maintaining infection of the host and thereby have utility in anti-bacterial therapy.
Clearly, there is a need for factors, such as the novel compounds of the invention, that have a present benefit of being useful to screen compounds for antibiotic activity. Such factors are also useful to determine their role in pathogenesis of infection, dysfunction and disease. There is also a need for identification and characterization of such factors and their antagonists and agonists which can play a role in preventing, ameliorating or correcting infections, dysfunctions or diseases.
The polypeptides of the invention have amino acid sequence homology to a known B. subtilis phoH protein.